Void suppressive lithium anodes for all-solid-state batteries

The all-solid-state lithium metal battery is a promising next-generation energy-storage technology due to it offering high energy density and safety. However, the issues of void formation and dendrite growth both remain unsolved. Here we demonstrate that void formation is controlled by the product of lithium full stripping areal capacity and applied current density, which we define as the void suppression capability (VSC). The VSC is enhanced by increasing self-diffusivity and initial lithium atom concentration. Using a Mg-1 wt% La inoculant in molten lithium (LiMgLa) to refine grains, lithium self-diffusivity and VSC are enhanced, resulting in an increase in the critical current density/capacity from 1.2 mA cm^-2/0.6 mAh cm^-2 for the LiMg anode to 2.2 mA cm^-2/1.1 mAh cm^-2 for the LiMgLa anode. The LiMgLa anodes enable stable lithium plating/stripping for over 1,200 h at 0.7 mA cm^-2 at room temperature. Phase-field modelling shows that the interfacial overpotential will be higher than the critical overpotential of the electrolyte when the stripped capacity is larger than 70% of the full depletion capacity, leading to dendrite growth and cell failure. Our observations offer a route to the design of all-solid-state lithium metal batteries with high powers and energy densities.